Bomb sight



M. F. BATES BOMB SIGHT Dec. 2,1930.

Filed June 1, 1926 2 Sheets-Sheet l INVENTOR merffiafes. ATZR N E Y Dec. 2, 1930. BATES 1,783,769

BOMB S IGHT Filed June 1, 1926 2 Sheets-Sheet 2 87 INVENTOR Momma/f. afea.

MXZTORN Patented Dec. 2, 1930 UNITED STATES PATENT OFFICE MORTIMER F. BATES, OF BROOKLYN, NEW YORK, ASSIGNOR, BY MESNE ASSIGNMENTS, TO SPERRY GYROSCOPE COMPANY, INC., OF BROOKLYN, NEW YORK, A CORPORATION Application filed June 1,

This invention relates to the optical system of stabilized bomb sights wherein the target is reflected by a prism or mirror tilting about a lateral axis and brought into focus in the plane of a stabilized reticule from which it is viewed through an eye-piece. In such bomb sights the apparent ground travel is followed by tilting the mirror about order to keep the target in sight, and in addition to add an additional correction to compensate for the drift angle or side drift of the projectile with respect to the target when dropped from the plane.

To accomplish the last named purpose, it has been the practice to provide means for shifting the stabilized reticule a small amount laterally, an amount which is a functionof the drift angle. This I regard as an objectionable feature of the present bomb sights inthat it requires adjustment of a delicate'stabilized part. In my invention I propose to leave the stabilized reticule fixed and to provide instead mechanism for tilting the mirror about a horizontal axis at an' angle to the aforesaid lateral axis, preferably about the longitudinal axis of the sight- This additional tilting of the mirror is preferably accomplished automatically according to a function of the angle through which the reticule is turned to keep its cross hairs parallel to the ground stream line. To ac complish this accurately, I interpose an automatic means for varying the amount of correction in accordance with the sight angle, or in other words, in accordance with the distance of the airplane from the target and height. It will, of course, be understood that the broad principles of my invention are applicable to other forms of sights than the particular form herein illustrated.

I also preferably provide means for introducing a separate tilt of the mirror about said fore and aft axis as an arbitrary offset smrrr 1926. Serial No. 112,811.

so that in case the target were obscured, and

the lateral distance of a visible object fromto turn right or left to maintain the desired.

course with respect to the ground. As a permanent correction for drift, I prefer to turn the sight about a vertical axis and to utilize this adjustment in connection with the movements of the mirror about a lateral axis in following the target to impart an additional adjustment to the mirror about the fore and aft axis to maintain the sight on the target in spite of the changing drift angle due to the approach of the plane to the target.

Referring to the drawings in which the preferred form of the invention is diagrammatically shown,

Fig. 1 is a diagrammatic layout showing the principal features of my invention.

Fig. 2 is a plan view, partly in section, of the mirror showing the means employed for tilting the same about the two axes and the linkage for automatically varying the offset in accordance with the sight angle.

Fig. 3 is a side elevation of the correction linkage of Fig. 2.

Fig. 4 is a detail sectional view of the freely slidable pin connected to the three slotted links taken on line 4-4 of Fig. 3.

Fig. 5 is a detail of the preferred form of handle for following the target when drift -is present.

Referring to Fig. 1, substantially all the mechanism therein shown diagrammatically except the electrical indicator 1, is a part of the bomb sight itself and is mounted so that it can be turned bodily around the vertical 1 9 mounted as shown in Fig. 1 no other means fiector or sight directing member 8 from the ground. The direction of the fore and aft line of the aircraft is represented by the arrow 9. To follow an object on the ground, therefore, the mirror is made tiltable about the transverse axis 10, the mirror being pivoted in the frame 11 and tiltable by any suitable means. When side drift is present, the target is kept in sight and the various corrections incident to a side wind are introduced by turning the bomb sight (and therefore the mirror 8) or other reflector about a vertical axis.

By my invention, on the other hand, in order to compensate for the various corrections necessitated by side drift and also preferably in order to keep the sight on the target, I also mount the mirror for adjustment about the fore and aft axis of the sight. As shown, this is accomplishedby pivotally mounting the frame 11 in bearings 25 and 26 and by adjusting the angle of said frame by gear 27 secured to the trunnion 28 on the frame 11. The tilting about the lateral axis 10 which is a secondary axis in the sense that it tilts'with the frame 11 about the primary axis 2526, is accomplished by means of the rod 12 fixed to the mirror 8 and link 13 pivotally mounted thereto at one end and hinged to the short link 14 at the other end. Link 14 is also hinged at 15 to shaft 16 of the gear sector 17. The latter is shown as geared to the second gear sector 18, which has a slot-ted arm 19 in the slot of which engages pin 20 on the adjustable block 21. Said block is shown as threaded on the shaft 22 which is rotated by any suitable means at a speed proportional to that of the aircraft so as to keep the line of sight directed on the target. As shown, the shaft may be rotated by the handle 23 or by a constant speed motor 24, the speed of which may be varied by any suitable means (not shown). By means of linkage 12 to 16, it will be seen that adjustment of the mirror about the fore and aft axis does not effect its adjustment about the lateral axis, since the axis 10-10 of the mirror is placed in line with the shaft 16. It should. be noted that with the mirror is needed to compensate for the varying effect of changes in the sight angle on the offset correction due to the fact that the lateral pivotal axis 10 of the mirror is a secondary axis and tilts with the frame 11. For efl'ecting the automatic offset to compensate for the drift angle or relative side drift of the projectile and target, I prefer to make use of the fact that the sight is turned about a is mounted tobe bodily rotated with the bomb sight about the large stationary gear 32. In

Fig. 1 gear 32 is shown as separated in two parts, but it will be-understood that it is preferably placed at the base of the bomb sight and that the shaft 31 is secured to the rotatable part thereof. When the bomb sight I is revolved about its vertical axis, therefore. the shaft 31 is revolved rotating the worm 32 thereon, thereby rotating the worm sector 33, shaft 34 and the slotted arm 35 thereon. The said arm carries a pin 36 which may be adjustable in said slot by means of the screw 37. The said pin fits in the second slotted arm 38 on shaft 39, said mechanism being for the purpose of adjusting the amount of offset to compensate for changes in the type of projectile affecting its terminal velocity.

The motion of the arm 38 and shaft 39 is shown as connected to one side 39 of a differential 40, the planetary arm of which is connected to a shaft 41, the purpose of the differential being to bring in other drift or ofl'set corrections as will be hereinafter explained.

The motion of the shaft 41 may be transmitted to tilt the mirror about its 1ongitudinal axis by any suitable means. As shown, the shaft 41 is provided with a slotted arm 50. while the shaft 49, which is geared by bevel gear 49' to bevel gear 27 of shaft 28, is provided with a slotted arm 48. It will be understood that as actually constructed any suitable gears and shafting may be placed between the shafts 28 and 29. In the construction shown, however, there is provided a floating pin 51 to connect the two slotted arms, said pin extending also-through a slot in downwardly projecting portion 47 of normally fixed member 46 (see also Figs. 3 and 4). Said member is shown as threaded on a shaft 42 which may be adjusted by wheel 43 so that the proper angular relationship between the shafts 41 and 49, for any given conditions may be set.

As above explained it is sometimes desirable where the target is obscured to sight on a visible object at a known distance to one side of the target so that while the sight is directed at said visible object the bomb will be dropped on the true target. For this purpose I have shown what I term an arbitrary ofl'set adjustment. This may be conveniently effected by means of a handle 60 serving to rotate the worm 61 which in turn turns the worm wheel 62. The amount of arbitrary offset may be indicated by any suitable means the manual adjustment.

' contact arm 79, said pointer being shown as p such as pointer 63 on the shaft 64 of said worm wheel, the said pointer being readable upon an arbitrary scale indicated diagrammatically at 65. This adjustment is shown as entering'one side of a second differential 66,the planetary arm 76 being secured to shaft 67. On said shaft is mounted bevel gear 68, meshing with 69 which is geared to the opposite side 69 of the differential 40 from the point at which the automatic offset comes in.

As above explained, the target may be followed when the airplane is side dirfting by directly turning the bomb sight bodily about its vertical axis. This is done in every case to establish preliminary alignment. It is, however, not entirely satisfactory to use this whole sight movement solely to \keep the target on the alignment wire 4, although it may be so operated if desired, as when the drift angle is once established the sight, as a whole, should not be disturbed. I, therefore, prefer to hold the target on the alignment wire 4 by introducing another means for temporarily tilting the mirror at will about the longitudinal axis of the sight and at the same time indicating to the pilot the amount and direction he should turn so that the actuating handle may again be brought to its mid-position and the mirror returned to its initial off-set adjustment. This adjustment I may refer to for convenience as This is shown as effected by the above mentioned handle 72 mounted on shaft -73 to which is secured gear 74 which turns through idler 75, the other side 75 of the differential 66, the planetary arm 76 thereof being secured to the shaft 67 as stated. It will be apparent,therefore, that the manual adjustment of the mirror to follow the target comes in through the same automatic compensating means for the sight angle as heretofore described so that the movement of the handle indicates accurately the direction and the amount of turn that the pilot should make to keep the target on the alignment wire 4.

In order to transmit thismovement to the pilot,I have'shown an electrical transmission system of the potentiometer type, the transmitterbeing shown as a resistance 78 over which is movable sliding contact 79 secured to shaft 73. Taps are led from the resistance and rotatable arm to the potentiometer indicator 80 and to battery 81 or other source ofE. M. F. It will be evidentthat the pointer 1 of the indicator will assume substantially the same angular position as the readable upon a suitable scale 82 showing the pilot whether to turn right or left and approximately the amountv of turn required.

Preferably the handle 72 is made automatically centralizing as by means of compression springs 83-84. Said springs are pref- 4 drift angle.

erably placed within a bore 85 in a fixed block 85' on which the shaft 73 is pivoted (see Fig. 5) and bear at their inner ends on slidable pistons 86 which in turn press on either side of the pin 87 secured to a depending portion 88 of the handle. The said pistons preferably have a fairly tight fit in the bores so that the centralizin action takes place slowly so that the horn er may correct the drift angle slightly if necessary by bodily turning the sight as handle 72 slowly centralizes of itself.

In =operating my invention, the bomber observes the target through the eye-piece 3. The shaft 22 is rotated either manually or by motor at the proper speed to keep the image of the target at the center of the reticule. If a side wind exists or if the target itself is moving across the apparent course of the airplane, the image will move to one side of the reticule and also the stream lines will flow at an angle to the cross hairs. As the bomber observes these conditions he preferably first rotates the bomb sight about its vertical axis so that the cross hairs are parallel to the ground stream lines. This results in the operation of the automatic off-set correction through the linkage 35 to 38 which gives the mirror the proper off-set angle forthe existing drift angle. This will, of course, tend to move the image out of the field of vision of the reticule. then rotates the handle 72 to tilt the mirror about its fore and aft axis until the image is again visible. This not only keeps the image of the target in View but also transmits to the pilot an indication of which way to change the heading of the craft so as to keep it flying directly toward the target. The pilot then brings the craft on to its new course, which is to one side of the original course, an amount determined by the automatic off-set corrections. If the stream lines are still at an angle to the reticule the bomber again adjusts the sight about the vertical axis, signalling again with the handle 72 and finally releasing the handle 72 whereupon it is slowly centralized as the adjustment takes place about the vertical axis. It will be understood that these adjustments may be made repeatedly until the final proper courseisreached when the plane will be flying a predetermined parallel course to the target to allow for side drift, under which conditions the angle between the heading of the craft and its ground course becomes the true As the shaft 22 is turned the proper correction is continuously introduced in both the automatic offset mechanism and the manual offset mechanism for the changing sight angle. If it is desired also, the

The bomber.

nav1gator can put in the arbitrary offset by 7 various features and elements in the combi-v nation and relations described, some of these may be altered and others omitted without interfering with the more general results outlined, and the invention extends to suchuse.

Having described my invention, what I claim and desire to secure by Letters Patent is:

1. In a bomb sight for aircraft, the combination with a sighting reticule, of a reflector for following the target, supporting means for said reticule and reflector mounted for turning about a vertical axis, means for mounting said reflector on said support to tilt about a transverse axis, means for mounting the same also for turning about a longitudinal axis, and means for adjusting said reflector about said last named axis.

2. In a bomb sight for aircraft, the combination with a reflector for following the target tiltable about a transverse axis, of means for mounting the same also for turning about a longitudinal axis, means for adjusting the sight about a vertical axis for side drift of the craft and means for adjusting said reflector about said longitudinal axis to give the sight an automatic offset for side drift of the bomb variable with the side drift of the craft.

3. In a bomb sight for aircraft, the combination with a sighting reticule, of a reflector for following the target, supporting means for said reticule and reflector mountedfor turning about a vertical axis, means for mounting said reflector on saidsupport to tilt about both major horizontal axes,'and means for adjusting said reflector about its longitudinal axis to give the sight at will an offset for the purpose specified.

4. In abombsight for aircraft, the combination with a sighting reticule, of a reflector for following the target, supporting means for said reticule and reflector mounted for turning about a vertical axis, means for mounting said reflector on said support to tilt about a transverse axis, means for mountin the reflector also for turning about a longltudinal axis, and means for adjusting said reflector about said last named axis to keep the target in the line of sight.

' 5. In a bomb sight for aircraft, the combination with the reflector for following the target tiltable about a transverse axis, of means for mounting the same also for turning about a longitudinal axis, means for adjusting said reflector about said last named axis to keep the target in the line of sight, and means for transmitting from said adjusting means a change of course indication tothe pilot.

6. In a bomb sight for aircraft, the combination with the reflector for following the target, tiltable about a transverse axis, of means for mounting the same also for turning about a longitudinal axis, means for adjusting said reflector about said last named axis, and additional means for varying said adjustment in accordance with the sight angle or range.

7. In a bomb sight for aircraft, the combination with the reflector for following the target tiltable about a transverse axis, of means for mountin the same also for turning about a longitu inal axis, means for adjusting said reflector about said last named axis to give the sight an automatic offset for side drift of the bomb variable with the side drift of the craft, and additional means for giving said sight at will an arbitrary offset for the purpose specified.

8. In a bomb sight for aircraft, the combination with the reflector for following the target tiltable about a transverse axis. of

means for mounting the same also for turning about a longitudinal axis, means variable in accordance with the. sight angle, means variable in accordance with the drift angle, and means for'turning said reflector about said longitudinal axis in accordance with a. combination of said two variable means.

9. In a bomb sight for aircraft, manually settable means for imparting to the sight an offset angle, means for varying the relative effect of said first named means in altering the offset angle, and means for transmitting to the pilot the movements of said first named means.

10. In a bomb sight for aircraft, the combination with the reflector for following the target, tiltable about a transverse axis, of means for mounting the same also for turning about a longitudinal axis, manual means for adjusting said reflector about said last a named axis, and slowacting centralizlng means connect-ed to said adjusting means.

11. In a bomb sight for aircraft, the combination with the reflector for following the target, tiltable about a transverse axis, of means for mounting the same also for turning about a longitudinal axis, manual means for adjusting said reflector about said last named axis, slow acting centralizing means connected to said adjusting means, and means for transmitting the movements of said adjusting means to the pilot. 4 p

12. In a bomb sight for aircraft, asightdirecting member, means for mounting the same for tilting about lateral and longitudinal horizontal axes and for adjustment about a vertical axis, rotatable means for turning the member about said lateral axis to maintain the proper sight angle, means for adjusting the same about its vertical axis to maintain the proper drift angle, and automatic means actuated in accordance with a function of the drift angle for adjusting the member about said longitudinal axis to maintain the proper offset angle for bomb dropping. V

13. In a bomb sight for aircraft, a sightdirecting member, means for mounting the same for tilting about lateral and longitudinal horizontal axesand for adjustment about a vertical axis, rotatable means for turning the member about said lateral axis to maintain the proper sight angle, means for temporarily tilting said member about said longitudinal axis to hold the target in the line of sight, means for adjusting the member about its vertical axis for permanently maintaining the proper drift angle, and automatic means generated by the release of said temporary means for giving the member a further adjustment about said longitudinal axis to maintain the proper ofiset to compensate for the drift angle.

14. In a bomb sight for aircraft, the combination with the sight-directing member for following the target, tiltable about a transverse axis, of means for mounting the same also for; turning about a longitudinal axis, manual means foradjusting said member about said last named axis, slow acting centralizing means connected to said adjust ing means, means for transmitting the move;

ments of said adjusting means to the pilot,

and means generated by the return movement of said centralizing means for adjusting the member about said longitudinal axis to maintain the proper offset for bomb. dropping.

15. In a bomb sight for aircraft, a sightdirecting member, means for mounting said member for turning about a vertical axis,

means for mounting said member for adjustment about both the fore and aft axis of the sight, and an axis at right an les thereto,

give said member the proper offset angle to compensate for the drift.

16. In a bomb sight for aircraft, a sightdirecting member, means for mounting said member for turning about a vertical axis, means for mounting said member fortilting about the fore and aft axis of the si ht, a secondary pivotal mounting within the rst mounting for mounting said member'for tilting about a normally transverse axis, means actuated by the turning of said member about its vertical axis for adjusting said member about said fore and aft axis to ofiset said member for side drift, the mounting of said member being such as to compensate for the varying eifect of the varying sight angle with the distance from the targeton the ofiset correction.

17. In a bomb sight, at sight-directing member mounted for turning abouta normally vertical axis and about the fore and aft axis of the sight and transversely thereof, and means for varying the offset angle of said member about said fore and aft axis as said signature.

MORTIMER BATES. 

